A projection objective for microlithography is disclosed, for example, in DE 198 59 634 A1 (U.S. Pat. No. 6,307,688) and US 2002/0163741 A1.
U.S. Pat. No. 5,852,518 presents a projection objective for microlithography with a rotatable mount technology. This reference discloses that one lens is rotated in a frame about an optical axis z relative to another lens. Both lenses have astigmatic surfaces. Imaging aberrations can be corrected via the rotating device. If a third-order deformation is present, for example in the case of a lens borne at three points, then this deformation can be compensated for at two lenses having the same deformation via corresponding rotation of the two lenses with respect to one another. This can be carried out with lenses having similar optical properties in the overall objective. It is possible to perform, for example, rotations through 60° in the case of a third-order deformation, whereby image aberrations are compensated for again.